The present invention relates to measurement of vertical angles and, more particularly, to a method of adjusting structure such as lighting fixtures mounted on towers to a desired light beam axis.
Runway approach lights are commonly mounted on towers in order to be placed at a desired elevation relative to the runway surface. It is also necessary that the individual beams of light be directed along an axis having a specific azimuth and elevation in order to be properly oriented with respect to the flight path of approaching aircraft. Adjustment of the lamp fixtures in their normal operating position is difficult because they are located at a height which is inaccessible from the ground. The towers are usually too fragile for climbing and the use of ladders, or the like, is also impractical or inconvenient.
Accordingly, it is necessary to adjust the position of the light bulbs or fixtures before the tower is erected to its operative position. Construction and mounting of the towers is such that the vertical angle of the major axis of the tower in the erected position is not precisely known. Therefore, adjustment of the light fixture relative to the tower axis with the tower in a lowered position will not necessarily result in a desired vertical angle of the light beam axis when the tower is erected.
The principal object of the invention is to provide a novel and highly accurate method of adjusting the angularity of a light source having an operative position normally inaccessible from ground level.
Another object is to provide a method of determining the vertical angle of an axis of an adjustable element when the element is in a position where direct reading of the angle is not practical.
Other objects will in part be obvious and will in part appear hereinafter.